Unifying dependencies to use syn 2. As per tower-rs/tower/issues/742.

[peter-lyons-kehl]

This makes all dependencies use syn crate version 2 (rather than both versions 1 and 2).

Why? syn is big. Even though most likely of recent syn 1 refers to/re-uses most of syn 2 (as per https://github.com/dtolnay/semver-trick by David Tolnay, the author of syn), having two major versions increases build times (in this case) by around 10%.

Most of Cargo.lock is generated due to cargo update:

❯ cargo update
    Updating crates.io index
    Updating async-trait v0.1.67 -> v0.1.68
    Updating axum v0.6.12 -> v0.6.18
    Updating axum-core v0.3.3 -> v0.3.4
    Updating futures-channel v0.3.27 -> v0.3.28
    Updating futures-core v0.3.27 -> v0.3.28
    Updating futures-task v0.3.27 -> v0.3.28
    Updating futures-util v0.3.27 -> v0.3.28
    Updating hermit-abi v0.2.6 -> v0.3.1
    Updating hyper v0.14.25 -> v0.14.27
    Removing log v0.4.17
    Updating mio v0.8.6 -> v0.8.8
    Updating num_cpus v1.15.0 -> v1.16.0
    Updating once_cell v1.17.1 -> v1.18.0
    Updating percent-encoding v2.2.0 -> v2.3.0
    Updating quote v1.0.26 -> v1.0.29
    Updating serde v1.0.158 -> v1.0.164
    Updating syn v2.0.5 -> v2.0.22
    Updating tracing-core v0.1.30 -> v0.1.31
    Updating unicode-ident v1.0.8 -> v1.0.9
    Updating want v0.3.0 -> v0.3.1
    Removing windows-sys v0.45.0
    Removing windows-targets v0.42.2
    Removing windows_aarch64_gnullvm v0.42.2
    Removing windows_aarch64_msvc v0.42.2
    Removing windows_i686_gnu v0.42.2
    Removing windows_i686_msvc v0.42.2
    Removing windows_x86_64_gnu v0.42.2
    Removing windows_x86_64_gnullvm v0.42.2
    Removing windows_x86_64_msvc v0.42.2

Also excluding .vscode/settings.json from GIT (not the whole .vscode folder, though, so devs can upload example config files, where useful.)